1. Field of the Invention
The present invention relates to a method of checking the function of an engine system having an internal combustion engine, e.g., checking of the function of an engine system installed in a motor vehicle after completion of the motor vehicle or after a repair, and particularly relates to the recognition of a malfunction based on adaptation values for a mixture adaptation or for a charge adaptation.
2. Description of the Related Art
Internal combustion engines are generally operated with the aid of a control unit. The control unit detects operating states of the internal combustion engine as well as environmental conditions, and receives an instruction from the driver, in particular in the form of a driver's intended torque. As a function of the provided variables, position sensors of the internal combustion engine, for example a position sensor for a throttle valve, a position sensor for fuel injectors, and other position sensors as well as the spark plugs for generating an ignition spark are controlled in order to operate the internal combustion engine in the intended manner.
The position of a position sensor intended by the control unit may differ from the actual position of the position sensor due to component tolerances and aging effects. In particular, with the aid of adaptation it is possible for control units to learn a deviation of the charge and of the mixture composition. Adaptation is used to modify the control variable which is output to the applicable position sensor and which causes displacement of the position sensor in such a way that the position of the position sensor intended by the provided control variable corresponds as closely as possible to the actual position of the position sensor, or that the effect of the position sensor intended by the provided control variable corresponds as closely as possible to the actual effect of the position sensor in the overall system.
The adaptation is carried out in that control variables provided by the control unit are acted on by adaptation values. The adaptation values include, for example, an offset adaptation value which acts on the control variable in an additive manner, and a slope adaptation value which acts on the control variable in a multiplicative manner.
In principle, the adaptation values are learned in multiple learning ranges. The learning ranges concern operating ranges of the internal combustion engine, which may be defined, for example, by an engine load at a rotational speed. In many cases, the additive offset adaptation value is learned in the idle operating range and the multiplicative slope adaptation value is learned in a partial load operating range. In driving mode of the motor vehicle, the adaptation values are appropriately adapted when the motor vehicle is operated in these operating ranges.
Based on the adaptation values thus obtained, various diagnostic functions are carried out via which errors in the engine system may be recognized and communicated to the driver. The error may also be stored in an error memory so that the error memory may be read out in a repair shop.
During manufacture of the motor vehicle, at the end of the assembly line it is desirable to have the most rapid option possible for testing the manufactured motor vehicles for mixture or charge errors, i.e., to identify errors which may result in operation of the internal combustion engine which differs from an intended operation due to a malfunction of the throttle valve position sensor, the injector position sensor, and the like. Heretofore, at the end of the manufacturing assembly line for a motor vehicle the engine system is operated in an idle operating state in which an adaptation was carried out in order to learn the additive offset adaptation values for the mixture adaptation and the charge adaptation. For an additive offset adaptation value which is not equal to zero, this generally results in incorrect metering of the quantity of fuel injected by the injectors.
The engine system of the motor vehicle is then operated at a partial load operating point with the aid of a roller type test stand, and a new adaptation is carried out in order to learn a multiplicative slope adaptation value for the injection quantity. However, to correctly carry out the adaptation and to obtain a reliable value for the multiplicative control error, on the one hand the partial load operating point must be maintained long enough for the engine system to be able to reach a steady state at the operating point, and on the other hand the operating point must be run through multiple times so that a realistic adaptation value may be ascertained.
For this purpose, it is proposed in published German patent application document DE 10 2006 007 698 A1 that the adaptation method runs through two operating points multiple times in alternation in order to increase the accuracy of the adaptation. Effects which are more likely to result in an offset error are better separated from effects which result in a slope error. After the operating points are occupied multiple times, the correct additive offset adaptation values and the correct multiplicative slope adaptation values may be ascertained, so that the component tolerances of the components causing the deviation and the changes in components due to aging may be adapted.
Since each of the partial load operating points must be occupied for a specified period of time, for example for 30 seconds up to several minutes, before the adaptation is carried out, due to the multiple changes between the partial load operating points the above-described method requires a relatively long adaptation time before correct adaptation values are obtained which are suitable for establishing whether or not the motor vehicle is free of errors.
An object of the present invention, therefore, is to be able to identify as rapidly as possible, after the motor vehicle is completed or after a repair in the repair shop, whether or not the motor vehicle is free of errors.